JP2009016236A - Dye-sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell which is improved in extraction efficiency of photoelectrons injected into a porous semiconductor membrane by optimally designing the composition and coloring matter of the porous semiconductor membrane adsorbing the coloring matter, and, in addition, has high efficiency. <P>SOLUTION: The dye-sensitized solar cell has a structure including: an anode electrode, on which a layer consisting of a porous semiconductor membrane layer adsorbing at least a sensitizing dye is formed on a surface of a transparent conductive substrate; and a cathode electrode facing the porous semiconductor membrane layer of the anode electrode, in which an electrolyte is sealed between the two electrodes that are the anode and cathode electrodes, wherein the porous semiconductor membrane layer includes at least two semiconductor compositions having different energy levels of a conduction band and is layered so that the energy levels of the conduction band stepwise or sequentially decrease toward the transparent conductive substrate, and the porous semiconductor membrane layer adsorbs at least two sensitizing dyes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a dye-sensitized solar cell. More specifically, the present invention relates to a highly efficient dye-sensitized solar cell in which photoelectron extraction efficiency is improved by optimally using a semiconductor composition and a dye.

  Dye-sensitized solar cells have a structure that can be manufactured in a general printing process, and are expected to greatly reduce costs in terms of both materials and processes, and are attracting attention as next-generation solar cells following silicon, GaAs, and CIS systems. Collecting. In this dye-sensitized solar cell, the dye molecules adsorbed on the semiconductor surface absorb the sunlight, and so-called spectral enhancement is caused by electron injection from the dye LUMO (lowest orbital) to the semiconductor CB (conduction band). Do a feeling. Since the dye molecule is bonded to the semiconductor surface via an adsorbing group, it is generally considered to be a monomolecular layer. That is, in order to convert light incident on the solar cell into electrons with high efficiency, a technique for improving the light absorption ability of the dye is required. On the other hand, a major breakthrough was achieved by forming titanium oxide ultrafine particles as a porous film containing appropriate pores.

  By adsorbing a single molecule of a dye molecule on the particle surface in this porous film, the specific surface area of the light absorption / electron injection site can be increased to several thousand times, and the sunlight incident on the solar cell is efficiently used. Can be converted to electrons well. Electrons injected from the dye diffuse efficiently in the titanium oxide porous film and reach the transparent electrode. On the other hand, a dye that has lost electrons receives electrons from iodine ions in the electrolyte. Furthermore, the iodine ions that have passed the electrons receive the electrons on the counter electrode Pt substrate. The dye-sensitized solar cell drives an external circuit through this series of light absorption / oxidation reduction processes.

  A semiconductor electrode used for a dye-sensitized solar cell generally has a nanoporous structure mainly composed of titanium oxide. This titanium oxide film has characteristics that depend on the amount of dye adsorbed and hardly causes recombination of electrons and holes, which is an electron deactivation process, and is convenient for providing a nanoporous structure with a carrier transfer function. However, in the titanium oxide porous film, carriers (electrons) injected from the excitation dye repeatedly trap / detrap into shallow traps and reach the transparent conductive layer through a random diffusion process. In the process, loss such as recombination to the dye cation, deactivation due to bonding with holes in the semiconductor, and leakage to the electrolyte may occur.

As a method for efficiently collecting injected photoelectrons, a semiconductor layer is formed by a plurality of regions having different energy levels in the semiconductor layer, and the energy levels in the semiconductor layer are stepwise and / or in the charge carrier extraction direction. There is a dye-sensitized photoelectric conversion device (see, for example, Patent Document 1) characterized by having a continuously decreasing region. Here, the energy level of the conduction band of the semiconductor is graded in the charge carrier extraction direction, that is, toward the transparent conductive substrate, so that the injected photoelectrons can be utilized not only by thermal diffusion but also by using an electric field gradient. It is a technology that collects electricity efficiently. However, the effect was not fully discussed, and in fact the effect was small.
JP 2004-87148 A

  The present invention is to solve the conventional problems as described above, and its purpose is to optimize the composition of the semiconductor porous film to which the dye is adsorbed and the dye to be injected into the semiconductor porous film. Another object is to provide a dye-sensitized solar cell with improved photoelectron extraction efficiency and higher efficiency.

  The present invention solves the above-mentioned problems by optimally designing the composition of the semiconductor porous film to which the dye is adsorbed and the dye, and the technical disclosure is provided herein. Specific means will be described below.

  1. An anode electrode in which a layer composed of at least a semiconductor porous film layer on which a sensitizing dye is adsorbed is formed on the surface of a transparent conductive substrate; a cathode electrode facing the semiconductor porous film layer side of the anode electrode; and In the dye-sensitized solar cell having a configuration in which an electrolyte is sealed between the two electrodes of the anode electrode and the cathode electrode, the semiconductor porous film layer has at least two kinds of semiconductors having different energy levels in the conduction band It is laminated so that the energy level of the conduction band decreases stepwise or continuously toward the transparent conductive substrate, and at least two or more types of increase are added to the semiconductor porous film layer. A dye-sensitized solar cell, wherein a dye-sensitizing dye is adsorbed.

  2. 2. The dye-sensitized solar cell as described in 1 above, wherein the sensitizing dye comprises at least two kinds of dyes having different LUMO levels.

  3. 3. The dye-sensitized solar cell according to 1 or 2, wherein at least one of the sensitizing dyes is a dye represented by the following general formula (1) or the following general formula (2).

(Wherein X _{11 to} X ₁₄ and X _{21 to} X ₂₆ each independently represent an oxygen atom, a sulfur atom or a selenium atom, and R ₁₂ , R ₁₃ , R ₂₂ and R ₂₃ are each independently Hydrogen atom, alkyl group, cycloalkyl group, alkenyl group, aryl group, heterocyclic group, halogen atom, cyano group, nitro group, hydroxy group, mercapto group, carboxyl group, carbonyl group, oxycarbonyl group, carbamoyl group, alkoxy group , Heterocyclic oxy group, carbonyloxy group, urethane group, sulfoxyl group, sulfonyloxy group, amino group, sulfonylamino group, sulfamoylamino group, acylamino group, ureido group, sulfonyl group, sulfamoyl group, alkylthio group, arylthio group Or a heterocyclic thio group, and these substituents are further substituted by the substituents shown above. May be. Moreover, R _12, R _13, and R _22, R ₂₃ good .R ₁₄ be bonded to form a ring structure, respectively represent a -COOH group or a -PO ₃ H ₂ group , R ₂₄ and R _{26 each} represent a hydrogen atom, —COOH group or —PO ₃ H ₂ group, and at least one represents a —COOH group or —PO ₃ H ₂ group, L ₁₁ , L ₂₁ and L ₂₂ represent Each independently represents a methylene group, an ethylene group or a propylene group, R ₁₅ and R _{25 each} represents a substituted or unsubstituted alkyl group, and R ₁₁ and R ₂₁ represent R ₁₂ , R ₁₃ and R ₂₂ , R Represents a group having the same meaning as _23. n represents an integer of 1 to 4.)
4). At least two kinds of semiconductor compositions having different energy levels of the conduction bands are formed by metal doping, and the metal-doped semiconductor composition is made of metal doping of different element types. 4. The dye-sensitized solar cell according to any one of 1 to 3 above.

  5. 4. The semiconductor composition according to any one of the above items 1 to 3, wherein at least two semiconductor compositions having different energy levels of the conduction bands are semiconductor compositions having at least two types having different doping amounts of the respective metal dopants. Dye-sensitized solar cell.

  6). The semiconductor composition having at least two or more different energy levels of the conduction band, at least one of which is composed of a single composition of titanium oxide, and the titanium oxide has the lowest energy level of the conductor. The dye-sensitized solar cell according to any one of 1 to 5.

  According to the present invention, by optimizing the composition of the semiconductor porous film to which the dye is adsorbed and the dye, the extraction efficiency of the photoelectrons injected into the semiconductor porous film is improved, and the dye-sensitized solar with higher efficiency is obtained. Batteries could be provided.

  The present invention will be described in more detail. First, the dye-sensitized solar cell of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing the basic structure of the dye-sensitized solar cell of the present invention. As shown in FIG. 1, the dye-sensitized solar cell of the present invention includes a transparent conductive base material 1 having a conductive layer 12 on a light-transmitting base material 11, a light absorption layer 21 on which dye molecules 3 are adsorbed, and It comprises a semiconductor porous membrane layer 2 comprising a light reflecting layer 22, a charge transfer layer (sometimes referred to as “electrolyte layer”) 4, and a counter substrate 6 having a cathode electrode 5. In FIG. 1, + represents a positive electrode, and-represents a negative electrode.

  When configuring the dye-sensitized solar cell of the present invention, the semiconductor porous membrane layer 2, the charge transfer layer 4 and the cathode electrode 5 are housed in a case with a sealant indicated by 7 in the figure. It is preferable to seal them or to seal them entirely with resin.

  When the solar cell of the present invention is irradiated with sunlight or an electromagnetic wave equivalent to sunlight, the dye 3 adsorbed on the semiconductor porous film layer 2 is excited by absorbing the irradiated sunlight or electromagnetic wave. The electrons generated by the excitation move to the semiconductor porous membrane layer 2 and are then supplied to the external circuit via the conductive layer 12. On the other hand, the electrons that have moved to the cathode electrode 5 by driving the external circuit reduce the redox electrolyte of the charge transfer layer 4. The dye 3 that has moved electrons to the semiconductor porous membrane layer 2 is an oxidant, but is reduced by being supplied with electrons from the cathode electrode 5 via the redox electrolyte of the charge transfer layer 4. At the same time, the redox electrolyte of the charge transfer layer 4 is oxidized and returned to a state where it can be reduced again by the electrons supplied from the cathode electrode 5. In this way, electrons flow and the dye-sensitized solar cell of the present invention can be configured.

  The semiconductor porous film layer of the present invention comprises at least two kinds of semiconductor compositions having different energy levels of conduction bands, and energy levels of the conduction bands stepwise or continuously toward the transparent conductive substrate. It is a feature that becomes lower. The semiconductor composition may be different element composition or the same element composition as long as there is a difference in the energy level of the conduction band, for example, semiconductor compositions having different element compositions, semiconductor compositions having different dopant types, semiconductor compositions having different dopant amounts, etc. Can be mentioned. Further, the energy level of the conduction band decreasing stepwise or continuously means that the semiconductor composition changes stepwise or continuously. The energy level can be graded by stacking the semiconductors having different compositions from each other or by continuously changing the ratio to form a porous film.

  Further, the present invention is characterized in that at least two or more sensitizing dyes are adsorbed together with the two or more semiconductor compositions. Hereinafter, the configuration of the conduction band energy level of the semiconductor and the sensitizing dye that are preferably applied to the present invention will be described with reference to FIG. FIG. 2 is a diagram simulating a semiconductor porous membrane layer adsorbed with the sensitizing dye of the present invention from the viewpoint of energy levels. The vertical straight line represents the surface of the transparent conductive substrate, and the arrow represents the energy level. The higher the level, the higher the energy level. The horizontal solid line represents the conduction band energy level of the semiconductor, and the dotted line represents the LUMO level of the sensitizing dye. In the present invention, the energy level of the conduction band is lowered stepwise or continuously toward the transparent conductive substrate, and the horizontal solid line is shown to become lower toward the left. Yes.

  FIG. 2 a) is a schematic view when one kind of sensitizing dye is adsorbed on a semiconductor porous film layer composed of two kinds of semiconductor compositions having different energy levels of conduction bands. When a semiconductor with a low conduction band and a semiconductor with a high conduction band are stacked, one type of dye optimized for a semiconductor with a low conduction band causes electron injection only in a semiconductor with a low conduction band, No electrons are injected. In b), the dye is optimized for a semiconductor having a high conduction band, and although electron injection occurs in both semiconductors, the high LUMO dye is preferable because the absorption spectrum becomes short and the loss becomes large in total. Absent. Ideally, a configuration in which a dye having an optimum LUMO level for each semiconductor is adsorbed is preferable. Specifically, the LUMO level of the sensitizing dye is preferably high with respect to the conduction band energy level of the semiconductor, preferably 0.1 to 0.6 eV high, and more preferably 0.2 to 0.4 eV high. . d) is an example in which the semiconductor composition is designed in three layers, and in this case as well, it is preferable to adsorb the optimum dye to each semiconductor.

  Hereinafter, these will be described in detail.

<Semiconductor porous membrane layer>
The porous body forming the semiconductor porous film layer according to the present invention is preferably composed of ceramic semiconductor fine particles typified by a metal oxide. The composition of the semiconductor fine particles is not particularly limited as long as the band gap between the valence band (VB) and the conduction band (CB) is about 3 eV, but a metal oxide is preferable in view of easy formation of the nanoporous film. As typical metal oxides, for example, titanium oxide, zinc oxide, tin oxide, indium oxide, niobium oxide, tungsten oxide, zirconium oxide, strontium titanate, barium titanate, calcium titanate, etc. can be raised, Of these, titanium oxide, zinc oxide, tin oxide, niobium oxide, and strontium titanate are preferable in view of the energy level of the conduction band and the adsorptivity of the dye, more preferably titanium oxide and zinc oxide, and most preferably titanium oxide. Further, in the present invention, for the purpose of improving the performance of the dye-sensitized solar cell, the semiconductor fine particles may be mixed, and further, the core-shell fine particles or composite formed by coating the semiconductor B on the surface of the semiconductor A. Fine particles may be used.

  In order to obtain the effects of the present invention, the metal oxide semiconductor is preferably doped with a metal element. As the metal element species, monovalent to pentavalent metal ion dopants can be selected. For example, Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe , Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb Bi, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. can be raised. The doping amount of the metal ion dopant is preferably 0.01 to 10 mol%, more preferably 0.1 to 5.0 mol%, and most preferably 0.1 to 1.0 mol% with respect to the number of metal atoms of the metal oxide semiconductor. . In order to obtain a sufficient effect, a doping amount of 0.01% or more is preferable, and a doping amount that is solid-solved in the semiconductor fine particles is preferably 10 mol% or less.

  As a method for producing semiconductor fine particles that can be used in the present invention, a generally known technique can be used. Fine particle forming methods are roughly classified into a vapor phase method and a liquid phase method. The gas phase method is a method of forming crystals from a gaseous source material, and is suitable for mass production of low-cost, high-purity particles that are easy to construct a continuous process. On the other hand, the liquid phase method is a method in which one kind of raw material or two or more kinds are mixed in a solution and particles are formed by utilizing the solubility change of the raw material and the product. The single jet method, double jet method, sol -Gel method is used, and it is widely used as a method for synthesizing high-quality fine particles with uniform particle shapes that are not suitable for extreme mass production. It is also a kind of liquid phase method, such as a melt method in which raw material is melted and particles are formed by utilizing the change in solubility during cooling, and a method in which it is formed in a flux salt melted at a high temperature in the same manner as the melt method. It is done.

  The semiconductor fine particles used in the light absorption layer of the present invention may be formed by any of the above methods as long as the particle size can be controlled, but the semiconductor composition can be easily controlled and the particle size can be controlled. The sol-gel method is preferably used for the reason that uniform high quality fine particles can be synthesized. The particle formation method using the sol-gel method hydrolyzes an organometallic compound using an acid or the like as a catalyst, and nucleates to grow particles in a liquid phase by a continuous condensation reaction to obtain desired metal oxide fine particles. It is a technique to obtain.

  An organometallic compound is a compound in which a metal and an organic substance are covalently bonded, coordinated or ionically bonded, and examples thereof include metal alkoxides, metal acylates, metal chelates, organometallic salts, and halogen metal compounds. In view of reactivity and stability, metal alkoxides are preferably used.

  The organometallic compound useful in the present invention is preferably a compound represented by the following general formula, but is not limited thereto.

[General Formula] M (R ₁ ) _x (R ₂ ) _y (R ₃ ) _z
In the above general formula, M is a metal (for example, Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga , Ge, Rb, Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb, Bi, Ce, Pr, Nd, Pm , Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc.), R ₁ is an alkyl group, R ₂ is an alkoxy group, R ₃ is a β-diketone coordination group, β-ketocarboxylate ester A group selected from a coordinating group, a β-ketocarboxylic acid coordinating group and a ketooxy group (ketooxy coordinating group), where the valence of the metal M is m, x + y + z = m, and x = 0 to m, Or x = 0 to m−1, y = 0 to m, z = 0 to m, and both are 0 or It is a positive integer.

Examples of the alkyl group represented by R ₁ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkoxy group represented by R ₂ include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a 3,3,3-trifluoropropoxy group. Further, a hydrogen atom in the alkyl group may be substituted with a fluorine atom. The group selected from the β-diketone coordination group, β-ketocarboxylic acid ester coordination group, β-ketocarboxylic acid coordination group and ketooxy group (ketooxy coordination group) represented by R ₃ includes β-diketone coordination group Examples of the group include 2,4-pentanedione (also referred to as acetylacetone or acetoacetone), 1,1,1,5,5,5-hexamethyl-2,4-pentanedione, 2,2,6,6-tetra Methyl-3,5-heptanedione, 1,1,1-trifluoro-2,4-pentanedione, and the like. Examples of β-ketocarboxylic acid ester coordination groups include, for example, acetoacetic acid methyl ester, acetoacetic acid And ethyl ester, propyl acetoacetate, ethyl trimethylacetoacetate, methyl trifluoroacetoacetate and the like, β-ketocarboxylic acid Examples of the coordinating group include acetoacetic acid, trimethylacetoacetic acid and the like, and examples of the ketooxy coordinating group include acetooxy group (or acetoxy group), propionyloxy group, butyryloxy group, acryloyloxy group, methacryloyloxy group. Etc. The number of carbon atoms in these groups is preferably 18 or less including the above-mentioned organometallic compounds. Further, as illustrated, it may be linear or branched, or a hydrogen atom substituted with a fluorine atom.

In the present invention, from the viewpoint of handling, an organometallic compound with a low risk of explosion is preferable, and an organometallic compound having at least one oxygen in the molecule is preferable. Organometallic compound containing at least one alkoxy group as such R2, or R ₃ of the beta-diketone coordinating group, beta-ketocarboxylic acid ester coordinating group, beta-keto carboxylic Sanhai position group and Ketookishi group A metal compound having at least one group selected from (ketoxy coordination group) is preferred.

  Specific organometallic compounds are shown below.

  Examples of organic titanium compounds include organic titanium compounds, titanium hydrogen compounds, and titanium halides. Examples of organic titanium compounds include triethoxy titanium, trimethoxy titanium, triisopropoxy titanium, tributoxy titanium, tetraethoxy titanium, Tetraisopropoxy titanium, methyldimethoxy titanium, ethyl triethoxy titanium, methyl triisopropoxy titanium, triethyl titanium, triisopropyl titanium, tributyl titanium, tetraethyl titanium, tetraisopropyl titanium, tetrabutyl titanium, tetradimethylamino titanium, dimethyl titanium di ( 2,4-pentanedionate), ethyltitanium tri (2,4-pentanedionate), titanium tris (2,4-pentanedionate), titanium tris (acetomethylaceta) G), triacetoxy titanium, dipropoxypropionyloxy titanium, etc., dibutylyloxy titanium, titanium hydrogen compound as monotitanium hydrogen compound, dititanium hydrogen compound, etc., and halogenated titanium as trichlorotitanium, tetrachlorotitanium, etc. Any of these can be preferably used in the present invention. Two or more of these may be mixed and used at the same time.

  Examples of tin compounds include organic tin compounds, tin hydrogen compounds, and tin halides. Examples of organic tin compounds include tetraethyltin, tetramethyltin, di-n-butyltin diacetate, tetrabutyltin, and tetraoctyltin. , Tetraethoxytin, methyltriethoxytin, diethyldiethoxytin, triisopropylethoxytin, diethyltin, dimethyltin, diisopropyltin, dibutyltin, diethoxytin, dimethoxytin, diisopropoxytin, dibutoxytin, tin dibutyrate, tin Examples of diacetacetonate, ethyltin acetoacetonate, ethoxytin acetoacetonate, dimethyltin diacetoacetonate, tin hydrogen compounds, etc., and tin halides include tin dichloride and tin tetrachloride.

  Examples of the organosilicon compound include tetraethylsilane, tetramethylsilane, tetraisopropylsilane, tetrabutylsilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, diethylsilanedi (2 , 4-pentanedionate), methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, etc., as silicon hydrogen compounds, tetrahydrogen silane, hexahydrogen disilane, etc., as halogenated silicon compounds, tetrachlorosilane , Methyltrichlorosilane, diethyldichlorosilane and the like, and any of them can be preferably used in the present invention.

  Examples of organic zirconium compounds include zirconium ethoxide, zirconium isopropoxide, zirconium n-propoxide, zirconium n-butoxide, zirconium t-butoxide, zirconium 2-ethylhexyl oxide, zirconium 2-methyl-2-butoxide, tetrakis (trimethyl). Siloxy) zirconium, zirconium di-n-butoxide (bis-2,4-pentanedionate), zirconium diisopropoxide bis (2,2,6,6-tetramethyl-3,5-heptanedionate, zirconium dimethacrylate Dibutoxide, zirconium hexafluoropentanedionate, zirconium methacryloxyethyl acetoacetate tri-n-propoxide, zirconium 2,4-pe Tanjioneto, zirconium 2,2,6,6-tetramethyl-3,5-heptanedionate, zirconium trifluoro pentanedionate, and the like.

  Examples of the aluminum alkoxide include aluminum (III) n-butoxide, aluminum (III) s-butoxide, aluminum (III) t-butoxide, aluminum (III) ethoxide, aluminum (III) isopropoxide, aluminum (III ) S-butoxide bis (ethyl acetoacetate), aluminum (III) di-s-butoxide ethyl acetoacetate, aluminum (III) diisopropoxide ethyl acetoacetate, aluminum (III) ethoxyethoxy ethoxide, aluminum hexafluoropenta Dionate, aluminum (III) 3-hydroxy-2-methyl-4-pyronate, aluminum (III) 9-octadecenyl acetoacetate diisopropoxide, aluminum (III) 2,4-pe Tanjioneto, aluminum (III) phenoxide, and aluminum (III) 2,2,6,6-tetramethyl-3,5-heptanedionate.

  Other organometallic compounds include, for example, niobium isopropoxide, antimony ethoxide, arsenic triethoxide, barium 2,2,6,6-tetramethylheptanedionate, beryllium acetylacetonate, bismuth hexafluoropentanedionate. , Dimethylcadmium, calcium 2,2,6,6-tetramethylheptanedionate, chromium trifluoropentanedionate, cobalt acetylacetonate, copper hexafluoropentanedionate, magnesium hexafluoropentanedionate-dimethyl ether complex, gallium ethoxy , Tetraethoxygermane, tetramethoxygermane, hafnium t-butoxide, hafnium ethoxide, indium acetylacetonate, indium 2,6-dimethyl Minoheptanedionate, ferrocene, lanthanum isopropoxide, lead acetate, tetraethyllead, neodymium acetylacetonate, platinum hexafluoropentanedionate, trimethylcyclopentadienylplatinum, rhodium dicarbonylacetylacetonate, strontium 2,2,6 , 6-tetramethylheptanedionate, tantalum methoxide, tantalum trifluoroethoxide, tellurium ethoxide, tungsten ethoxide, vanadium triisopropoxide oxide, magnesium hexafluoroacetylacetonate, zinc acetylacetonate, diethylzinc, etc. Is mentioned.

  The semiconductor porous membrane layer of the present invention is characterized by comprising at least two kinds of semiconductor compositions having different energy levels of conduction bands, and the sol-gel reaction is carried out by mixing the above organometallic compounds alone or in combination of two or more kinds. By doing so, it is possible to obtain semiconductor fine particles in which the energy level of the conductor is controlled. The semiconductor composition can also be controlled by directly doping metal ions during the sol-gel reaction using the organometallic compound.

  Next, the solvent used for the sol-gel reaction will be described. The solvent uniformly mixes each component in the sol solution, and at the same time prepares the solid content of the composition of the present invention, so that it can be applied to various coating methods to improve the dispersion stability and storage stability of the composition. Is. These solvents are not particularly limited as long as they can fulfill the above purpose. Preferable examples of these solvents include water and organic solvents that are highly miscible with water.

  Examples of organic solvents include tetrahydrofuran, dimethoxyethane, formic acid, acetic acid, methyl acetate, alcohols (methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, tert-butyl alcohol), ethylene glycol, diethylene glycol, triethylene glycol , Ethylene glycol monobutyl ether, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide and the like.

  During the sol-gel reaction, the metal alkoxide is hydrolyzed and polycondensed in water and an organic solvent. At this time, it is preferable to use a catalyst in order to promote the reaction. As a catalyst for hydrolysis, an acid is generally used. As the acid, an inorganic acid or an organic acid is used. Inorganic acids include hydrochloric acid, hydrogen bromide, hydrogen iodide, sulfuric acid, sulfurous acid, nitric acid, phosphoric acid, and organic acid compounds include carboxylic acids (formic acid, acetic acid, propionic acid, butyric acid, succinic acid, trifluoroacetic acid, perfluoro Octanoic acid, benzoic acid, phthalic acid, etc.), sulfonic acids (methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid), p-toluenesulfonic acid, pentafluorobenzenesulfonic acid, etc.), phosphoric acid / phosphonic acid (phosphoric acid dimethyl ester) , Phenylphosphonic acid, etc.), Lewis acids (boron trifluoride etherate, scandium triflate, alkyl titanic acid, aluminate, etc.), heteropolyacids (phosphomolybdic acid, phosphotungstic acid, etc.), and the like.

  The semiconductor porous membrane layer of the present invention preferably has a structure in which a light absorption layer and a light reflection layer are laminated in order from the light transmissive substrate side, and the light reflection layer has an aspect ratio (hereinafter sometimes abbreviated as AR). Is more preferably 3 or more shape anisotropic fine particles. Examples of the shape anisotropic fine particles include particles having shape anisotropy such as flat plate shape, flake shape, plate shape, needle shape, columnar shape, fiber shape, rugby ball shape, spindle shape, etc. , Flake-like and plate-like, and the plate-like shape is most preferred from the light reflectivity. The preferred aspect ratio is 3 or more and 200 or less, and more preferably 10 or more and 100 or less. The light absorption layer of the present invention preferably has an average particle diameter of 5 nm to 100 nm which does not substantially scatter sunlight, and more preferably 8 nm to 80 nm, and 10 nm to 30 nm from the specific surface area and void size. The reflective layer preferably has an average particle diameter of 100 nm to 10 μm for reflecting sunlight, more preferably about 200 nm to 3 μm, and most preferably about 250 nm to 2 μm from the viewpoint of reflection efficiency and conversion efficiency.

  The average particle diameter of the present invention is a circle equivalent diameter when the projected area of particles observed with a transmission electron microscope (for example, JEM-2010F type manufactured by JEOL Ltd.) is converted into a perfect circle, and the number of observed particles is 500. The average equivalent circle diameter is shown above. In the present invention, the aspect ratio indicates a value obtained by dividing the average particle diameter by an average thickness obtained by observing 500 or more particles from the lateral direction.

  Here, the fact that sunlight is not substantially scattered means that visible light (mainly 400 nm to 780 nm light) contained in sunlight, ultraviolet light called UVA (315 nm to 400 nm light), near infrared light to far light. It means that spectral light including infrared rays (light of 780 nm or more) is not scattered. This wavelength region can be classified by Mie scattering, and the scattering characteristics are affected by the wavelength of light, particle diameter, and particle refractive index. In the case of inorganic fine particles, it is generally said that scattering occurs when a particle size comparable to the wavelength is present. Experimentally, it can be confirmed by simulating the average radiant energy of sunlight observed in the temperate region and evaluating the haze value of the semiconductor porous film with spectrum light called air mass 1.5 (AM1.5). .

  Regarding the semiconductor porous membrane layer of the present invention, the thickness of the light absorption layer is particularly preferably 5 μm to 20 μm, more preferably 8 μm to 18 μm, and most preferably 11 μm to 15 μm because of the highest conversion efficiency. . The light reflecting layer can be designed with a thickness of about 0.5 μm to 10 μm, preferably 1 μm to 5 μm, and more preferably 1 μm to 3 μm. If the thickness of the light reflecting layer is too thin, sufficient light reflectivity cannot be obtained. On the other hand, if the thickness is too thick, the thickness of the semiconductor porous membrane layer itself is increased and the diffusion of the electrolyte is inhibited. There is a possibility that the recombination chance between the electrons injected into the dye and the dye hole is increased and the Voc is lowered. Furthermore, the total thickness of the semiconductor porous film layer including the light absorption layer and the light reflection layer is preferably about 10 μm to 20 μm, more preferably about 13 μm to 17 μm, and most preferably 14 μm to 16 μm.

  Next, the manufacturing method of the semiconductor porous film of this invention is demonstrated.

As a method for producing the semiconductor porous film, it is possible to apply a known method,
(1) A method of forming a semiconductor layer by applying a suspension containing semiconductor fine particles on a conductive substrate, drying and firing,
(2) Electrophoretic electrodeposition method in which a conductive substrate is immersed in a colloidal solution, and semiconductor fine particles are adhered to the conductive substrate by electrophoresis.
(3) A method in which a foaming agent is mixed and applied to a colloidal solution or dispersion and then sintered to make it porous.
(4) After the polymer microbeads are mixed and applied, a method of removing the polymer microbeads by heat treatment or chemical treatment to form voids and making it porous can be applied.

  Among the above-described production methods, a known method can be applied particularly as a coating method, and examples include a screen printing method, an ink jet method, a roll coating method, a doctor blade method, a spin coating method, and a spray coating method. Can do.

  In particular, in the case of the above method (1), the particle diameter of the semiconductor fine particles in the suspension is preferably finer and is preferably present as primary particles.

  The semiconductor porous membrane layer of the present invention is characterized by comprising at least two kinds of semiconductor compositions having different energy levels of conduction bands, and is conducted stepwise or continuously toward the transparent conductive substrate. The band is characterized by a lower energy level. For example, a plurality of layers having different semiconductor compositions may be laminated by using the above-described coating method, or two or more kinds of semiconductor fine particle dispersions may be continuously sprayed at different ratios. A semiconductor porous film layer designed so that the energy level of the conductor is lowered can be formed.

  The suspension containing the semiconductor fine particles can be prepared by dispersing the semiconductor fine particles in a solvent.

  The solvent is not particularly limited as long as it can disperse the semiconductor fine particles, and includes water, an organic solvent, and a mixed solution of water and an organic solvent.

  As the organic solvent, alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone, acetone and acetyl acetone, hydrocarbons such as hexane and cyclohexane, and the like are used. In the suspension, a surfactant, a viscosity modifier (polyhydric alcohol such as polyethylene glycol), a dispersant and the like can be added as necessary. The concentration range of the semiconductor fine particles in the solvent is preferably 0.1% by mass to 70% by mass, and more preferably 0.1% by mass to 30% by mass.

  The above paste is preferably sufficiently primary particles using a known disperser. Examples of the disperser that can be used in the present invention include an ultrasonic disperser, a bead mill disperser, and a roll mill disperser, and can be appropriately selected depending on the dispersion step and the viscosity of the paste.

  The suspension containing the semiconductor fine particles obtained as described above is applied on a conductive substrate, dried, etc., and then baked in air or in an inert gas. A metal oxide semiconductor layer is formed.

  The semiconductor porous film layer obtained by applying and drying a suspension on a conductive substrate is composed of an aggregate of semiconductor fine particles, and the particle size of the fine particles is the primary particle size of the semiconductor fine particles used. It depends. The semiconductor porous membrane layer formed on the conductive substrate is a mechanically fragile film having a weak bonding force with the conductive substrate and a bonding force between the fine particles. It is preferable to increase the mechanical strength by baking treatment to obtain a fired product film that is strongly fixed to the substrate.

  By carrying out the firing process at the same time, so-called necking due to fusion adhesion is formed between the particles, and the effect of improving the electron conductivity in the semiconductor porous film is obtained.

  In the present invention, the fired product film may have any structure, but preferably has a porous structure (also referred to as a porous layer having voids).

  Here, the porosity of the semiconductor porous membrane layer is preferably 10% by volume or less, more preferably 8% by volume or less, and particularly preferably 0.01% by volume to 5% by volume.

  The porosity of the semiconductor porous film layer means a porosity that is penetrating in the thickness direction of the dielectric, and can be measured using a commercially available device such as a mercury porosimeter (for example, Shimadzu Polarizer 9220 type). I can do it.

  The firing temperature is about 300 ° C. to 1000 ° C. However, in the case of titanium oxide, care must be taken because the crystal phase obtained varies depending on the firing temperature.

  When titanium oxide is used in the present invention, it is generally preferable to use an anatase crystal formed at a temperature of 600 ° C. or lower in order to form a photocatalytically inactive rutile crystal at a firing temperature of 900 ° C. or higher.

  The semiconductor porous membrane layer of the present invention is, for example, titanium tetrachloride for the purpose of increasing the surface area of the semiconductor fine particles after the baking treatment, and for increasing the electron conductivity between the semiconductor fine particles and the substrate electrode, or between the semiconductor fine particles. Chemical plating using an aqueous solution or electrochemical plating using a titanium trichloride aqueous solution may be performed.

<Dye>
In the present invention, the dye 3 adsorbed on the surface of the semiconductor porous membrane layer 2 described above has absorption in various visible light regions and / or infrared light regions, and is the lowest higher than the conduction band of the metal oxide semiconductor. A dye having an empty level is preferable, and various known dyes can be used. For example, azo dyes, quinone dyes, quinone imine dyes, quinacridone dyes, squarylium dyes, cyanine dyes, cyanidin dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes, porphyrin dyes, perylene dyes Examples thereof include dyes, indigo dyes, phthalocyanine dyes, naphthalocyanine dyes, rhodamine dyes, and rhodanine dyes. Metal complex dyes are also preferably used. In this case, Cu, Ni, Fe, Co, V, Sn, Si, Ti, Ge, Cr, Zn, Ru, Mg, Al, Pb, Mn, In, Mo Y, Zr, Nb, Sb, La, W, Pt, Ta, Ir, Pd, Os, Ga, Tb, Eu, Rb, Bi, Se, As, Sc, Ag, Cd, Hf, Re, Au, Ac Various metals such as Tc, Te, and Rh can be used.

  Of the above, polymethine dyes such as cyanine dyes, merocyanine dyes, and squarylium dyes are one preferred embodiment. Specifically, JP-A-11-35836, JP-A-11-67285, and JP-A-11-86916. JP-A-11-97725, JP-A-11-158395, JP-A-11-163378, JP-A-11-214730, JP-A-11-214731, JP-A-11-238905, JP-A-2004-207224 And dyes described in each specification such as JP-A No. 2004-319202, European Patent No. 892411 and No. 911841. Furthermore, a metal complex dye is also one preferred embodiment, and a metal phthalocyanine dye, a metal porphyrin dye or a ruthenium complex dye is preferable, and a ruthenium complex dye is particularly preferable. Examples of ruthenium complex dyes include U.S. Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440, JP-A-7-249790, JP-A-10-504512, WO 98/50393. And complex dyes described in each specification such as JP-A No. 2000-26487, JP-A No. 2001-223037, JP-A No. 2001-226607, JP-A No. 3430254, and the like.

  These dyes preferably have a large extinction coefficient and are stable against repeated redox. The dye is preferably chemically adsorbed on the metal oxide semiconductor and has a functional group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amide group, an amino group, a carbonyl group, or a phosphine group. preferable.

  The dye used in the present invention is characterized by being adsorbed on at least two kinds of the semiconductor porous membrane in the previous period, and can be appropriately selected from the dye examples described above. The two or more selected dyes preferably have at least different LUMO levels from each other, and more preferably selected optimally for the energy level of the conductor in the semiconductor composition.

  In the present invention, it is particularly preferable to use a rhodanine dye as the dye adsorbed on the surface of the metal oxide. Any structure can be used as long as it is a rhodanine dye, but it is particularly preferable to use at least one dye represented by the general formula (1) or the general formula (2). .

In the general formula (1) or the general formula (2), X _{11 to} X ₁₄ and X _{21 to} X ₂₆ each independently represent any of an oxygen atom, a sulfur atom, and a selenium atom, preferably X ₁₁ , X ₁₂ , X ₁₄ and X ₂₁ , X ₂₂ , X ₂₄ and X ₂₆ are each a sulfur atom or a selenium atom, more preferably a sulfur atom. X ₁₃ , X ₂₃ and X ₂₅ are preferably oxygen atoms. R ₁₂ , R ₁₃ , R ₂₂ and R ₂₃ each independently represents a hydrogen atom or a substituent. R ₁₄ represents a —COOH group or —PO ₃ H ₂ group, R ₂₄ and R ₂₆ represent a hydrogen atom, —COOH group or —PO ₃ H ₂ group, and at least one of them represents a —COOH group or —PO ₃ H group. ₂ groups are represented. L ₁₁ and L ₂₁ and L ₂₂ each independently represent a divalent linking group. Examples of the divalent linking group include a methylene group (—CH ₂ —), an ethylene group (—CH ₂ CH ₂ —), a propylene group (—CH ₂ CH ₂ CH ₂ —), and the like. A methylene group and an ethylene group; R ₁₅ and R _{25 each} represents a substituted or unsubstituted alkyl group, preferably a linear or branched alkyl group having 1 to 8 carbon atoms, and a linear or branched alkyl group having 2 to 4 carbon atoms (for example, an ethyl group). , I-propyl group, n-butyl group and the like) are more preferable.

Examples of substituents such as R ₁₂ , R ₁₃ , R ₂₂ and R ₂₃ include alkyl groups (eg, methyl group, ethyl group, i-propyl group, t-butyl group, n-dodecyl group and 1-hexylnonyl group). Etc.), cycloalkyl groups (eg cyclopropyl group, cyclohexyl group, bicyclo [2.2.1] heptyl group and adamantyl group etc.) and alkenyl groups (eg 2-propylene group, oleyl group etc.), aryl groups (eg phenyl Group, ortho-tolyl group, ortho-anisyl group, 1-naphthyl group, 9-anthranyl group, etc.), heterocyclic group (for example, 2-tetrahydrofuryl group, 2-thiophenyl group, 4-imidazolyl group, 2-pyridyl group, etc.) ), Halogen atoms (eg fluorine atom, chlorine atom, bromine atom, etc.), cyano group, nitro group, hydroxy group, mercapto group, carboxyl group, Rubonyl group (for example, alkylcarbonyl group such as acetyl group, trifluoroacetyl group, pivaloyl group, arylcarbonyl group such as benzoyl group, pentafluorobenzoyl group, 3,5-di-t-butyl-4-hydroxybenzoyl group) Oxycarbonyl groups (for example, alkoxycarbonyl groups such as methoxycarbonyl group, cyclohexyloxycarbonyl group, n-dodecyloxycarbonyl group, phenoxycarbonyl group, 2,4-di-t-amylphenoxycarbonyl group, 1-naphthyloxycarbonyl group Aryloxycarbonyl groups such as 2-hydroxyloxycarbonyl group, heterocyclic oxycarbonyl groups such as 1-phenylpyrazolyl-5-oxycarbonyl group, etc.), carbamoyl groups (for example, dimethylcarbamoyl group, 4- (2,4-di) t-amylphenoxy) alkylcarbamoyl group such as butylaminocarbonyl group, arylcarbamoyl group such as phenylcarbamoyl group, 1-naphthylcarbamoyl group), alkoxy group (for example, methoxy group, 2-ethoxyethoxy group, etc.), aryloxy group ( For example, phenoxy group, 2,4-di-t-amylphenoxy group, 4- (4-hydroxyphenylsulfonyl) phenoxy group, etc.), heterocyclic oxy group (for example, 4-pyridyloxy group, 2-hexahydropyranyloxy group) ), Carbonyloxy groups (eg, alkylcarbonyloxy groups such as acetyloxy group, trifluoroacetyloxy group, pivaloyloxy group, aryloxy groups such as benzoyloxy group, pentafluorobenzoyloxy group), urethane groups (eg, N, N-dimethylow Alkyl urethane groups such as a letane group, aryl urethane groups such as an N-phenylurethane group, N- (p-cyanophenyl) urethane group), sulfoxyl groups, sulfonyloxy groups (for example, methanesulfonyloxy groups, trifluoromethanesulfonyloxy groups, alkylsulfonyloxy group such as n-dodecanesulfonyloxy group, arylsulfonyloxy group such as benzenesulfonyloxy group, p-toluenesulfonyloxy group, etc., amino group (for example, dimethylamino group, cyclohexylamino group, n-dodecylamino group, etc.) Alkylamino group, anilino group, arylamino group such as pt-octylanilino group), sulfonylamino group (for example, methanesulfonylamino group, heptafluoropropanesulfonylamino group, n-hexadecylsulfonylamino) Alkylsulfonylamino groups such as a group, arylsulfonylamino groups such as p-toluenesulfonylamino group and pentafluorobenzenesulfonylamino), sulfamoylamino groups (for example, alkylsulfa such as N, N-dimethylsulfamoylamino group) Moylamino group, arylsulfamoylamino group such as N-phenylsulfamoylamino group), acylamino group (eg, alkylcarbonylamino group such as acetylamino group, myristoylamino group, arylcarbonylamino group such as benzoylamino group), Ureido group (for example, alkylureido group such as N, N-dimethylaminoureido group, N-phenylureido group, arylureido group such as N- (p-cyanophenyl) ureido group), sulfonyl group (for example, methanesulfonyl group, trifluoride) Alkylsulfonyl group such as lomethanesulfonyl group and arylsulfonyl group such as p-toluenesulfonyl group), sulfamoyl group (for example, dimethylsulfamoyl group, 4- (2,4-di-t-amylphenoxy) butylaminosulfonyl group, etc.) Alkylsulfamoyl group, arylsulfamoyl group such as phenylsulfamoyl group), alkylthio group (eg methylthio group, t-octylthio group etc.), arylthio group (eg phenylthio group etc.) and heterocyclic thio group (eg 1-phenyltetrazole-5-thio group, 5-methyl-1,3,4-oxadiazole-2-thio group and the like). These substituents may be further substituted with the substituents shown above.

R ₁₂ , R ₁₃ , R ₂₂ and R ₂₃ may be bonded to each other to form a ring structure, and the formed ring structure may be either an aliphatic ring or an aromatic ring, Or a heterocyclic ring. The ring formed by bonding may be substituted with the substituent shown above, or may be further condensed with another ring structure. In general formula (1) or general formula (2), It may be further condensed with the represented compound itself.

Examples of the substituents for R ₁₂ , R ₁₃ , R ₂₂ , and R ₂₃ include those described above, and preferable examples are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an aryl group, and a heterocyclic ring. Group, an alkoxycarbonyl group, and more preferably a hydrogen atom, a substituted or unsubstituted alkyl group.

R ₁₁ and R ₂₁ represent any substituents, and can be the same substituents as R ₁₂ , R ₁₃ , R ₂₂ , and R ₂₃ described above, but at least one of them is electron withdrawing. In such a case, n represents an integer of 1 to 4. In the case of an electron-withdrawing substituent, the Hammett's substituent constant σp is preferably 0.1 or more and 0.8 or less, and the sum of the σp values of the substituents is preferably 0.1. It is preferably 2 or more and 2.0 or less, and most preferably 0.25 or more and 1.5 or less.

  As the value of Hammett's substituent constant σp here, Hansch, C .; It is preferable to use the values described in the report of Leo et al. (For example, J. Med. Chem. 16, 1207 (1973); ibid. 20, 304 (1977)).

  For example, a substituent or atom having a value of σp of 0.10 or more includes a chlorine atom, a bromine atom, an iodine atom, a carboxyl group, a cyano group, a nitro group, a halogen-substituted alkyl group (for example, trichloromethyl, trifluoromethyl, chloro Methyl, trifluoromethylthiomethyl, trifluoromethanesulfonylmethyl, perfluorobutyl), aliphatic / aromatic or heterocyclic acyl groups (eg formyl, acetyl, benzoyl), aliphatic / aromatic or heterocyclic sulfonyl groups (eg trifluoromethane) Sulfonyl, methanesulfonyl, benzenesulfonyl), carbamoyl groups (eg carbamoyl, methylcarbamoyl, phenylcarbamoyl, 2-chloro-phenylcarbamoyl), alkoxycarbonyl groups (eg methoxycarbonyl, ethoxycarbonyl) Bonyl, diphenylmethylcarbonyl), substituted aromatic groups (eg pentachlorophenyl, pentafluorophenyl, 2,4-dimethanesulfonylphenyl, 2-trifluoromethylphenyl), heterocyclic residues (eg 2-benzoxazolyl, 2-benzthiazolyl, 1-phenyl-2-benzimidazolyl, 1-tetrazolyl), azo group (eg phenylazo), ditrifluoromethylamino group, trifluoromethoxy group, alkylsulfonyloxy group (eg methanesulfonyloxy), acyloxy group ( For example, acetyloxy, benzoyloxy), arylsulfonyloxy group (eg benzenesulfonyloxy), phosphoryl group (eg dimethoxyphosphonyl, diphenylphosphoryl), sulfamoyl group (eg N-ethylsulfa) Moyl, N, N-dipropylsulfamoyl, N- (2-dodecyloxyethyl) sulfamoyl, N-ethyl-N-dodecylsulfamoyl, N, N-diethylsulfamoyl) and the like.

  Substituents with a σp value of 0.35 or more include cyano groups, nitro groups, carboxyl groups, fluorine-substituted alkyl groups (eg trifluoromethyl, perfluorobutyl), aliphatic / aromatic or heterocyclic acyl groups (eg acetyl) , Benzoyl, formyl), aliphatic / aromatic or heterocyclic sulfonyl groups (eg trifluoromethanesulfonyl, methanesulfonyl, benzenesulfonyl), carbamoyl groups (eg carbamoyl, methylcarbamoyl, phenylcarbamoyl, 2-chloro-phenylcarbamoyl), alkoxy Carbonyl group (for example, methoxycarbonyl, ethoxycarbonyl, diphenylmethylcarbonyl), fluorine or sulfonyl group substituted aromatic group (for example, pentafluorophenyl, 2,4-dimethanesulfonylphenyl), heterocyclic residue Such as 1-tetrazolyl), an azo group (e.g. phenylazo), an alkylsulfonyloxy group (e.g. methanesulfonyloxy), a phosphoryl group (e.g., dimethoxyphosphoryl, diphenylphosphoryl), a sulfamoyl group.

  Examples of the substituent having a value of σp of 0.60 or more include a cyano group, a nitro group, an aliphatic / aromatic or heterocyclic sulfonyl group (for example, trifluoromethanesulfonyl, difluoromethanesulfonyl, methanesulfonyl, benzenesulfonyl) and the like. .

R ₁₁ and R ₂₁ are preferably a halogen atom, a halogen-substituted alkyl group (such as a trifluoromethyl group), an alkoxycarbonyl group, a carbamoyl group, or a cyano group.

  The compound of the general formula (1) or the general formula (2) includes ions and salts derived from the compound in addition to the compound itself represented by the general formula. For example, when it has a sulfonic acid group in the molecular structure, it includes, in addition to the compound, an anion generated by dissociation of the sulfonic acid group, and a salt formed by the anion and a counter cation. Such a salt may be a salt formed with a metal ion such as sodium salt, potassium salt, magnesium salt or calcium salt, or an organic base such as pyridine, piperidine, triethylamine, aniline or diazabicycloundecene. It may be a formed salt. Similarly, in the case of a compound having a basic group in the molecule, a cation produced by protonation of the compound, and hydrochloride, sulfate, acetate, methylsulfonate, p-toluenesulfonate, etc. Also included are salts formed with acids.

  Specific examples of the compound represented by the general formula (1) or the general formula (2) in the present invention are shown below, but the content of the present invention is not limited to these exemplified compounds.

  The above-mentioned compounds of the present invention include, for example, “Myanine Soybean and Relayed Compounds” (1964, published by Inter Science Publishers), US Pat. No. 2,454,629, 2 , 493,748, JP-A-6-301136, 2003-203684 and the like, and can be synthesized with reference to conventionally known methods.

  These dyes preferably have a large extinction coefficient and are stable against repeated redox. The dye is preferably chemically adsorbed on the metal oxide semiconductor and has a functional group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amide group, an amino group, a carbonyl group, or a phosphine group. preferable.

  In the present invention, the method for adsorbing the dye to the semiconductor porous membrane layer is not particularly limited, and a known method can be used. For example, a method of dissolving a dye in an organic solvent to prepare a dye solution and immersing the semiconductor layer on the transparent conductive film in the obtained dye solution, or a method of applying the obtained dye solution to the surface of the semiconductor layer, etc. Can be mentioned. In the former, a deep method, a roller method, an air knife method or the like can be applied, and in the latter, a wire bar method, an application method, a spin method, a spray method, an offset printing method, a screen printing method, or the like can be applied. Prior to the adsorption of the dye, the surface of the semiconductor layer may be subjected to a treatment such as a decompression treatment or a heat treatment in advance to activate the surface and remove moisture in the film.

  From the viewpoint of preferably obtaining a sensitizing effect on the semiconductor layer, the time for immersing the semiconductor film in the dye solution is preferably 3 hours to 48 hours, and more preferably 4 hours to 24 hours.

  In addition, the dye solution may be heated to a temperature at which it does not boil as long as the dye does not decompose. The preferred temperature range is 10 ° C. to 50 ° C., particularly preferably 15 ° C. to 35 ° C., but this is not the case when the solvent boils in the temperature range as described above. Moreover, when making it adsorb | suck in the upper limit which boils, it is preferable to perform an adsorption | suction process on the conditions which a solvent does not deplete using a reflux apparatus etc.

  In addition, the dye solution in which the semiconductor film is immersed can be irradiated with ultrasonic waves. A commercially available apparatus can be used for the ultrasonic irradiation, and the irradiation time is preferably 30 minutes to 4 hours, more preferably 1 hour to 3 hours.

  The solvent used for the dye solution may be any solvent that dissolves the dye, and a conventionally known solvent can be used. In addition, the solvent is preferably a solvent purified in accordance with a conventional method, or a solvent having higher purity by performing distillation and / or drying as necessary prior to use of the solvent, for example, methanol, ethanol , Butanol, one or more hydrophobic solvents, aprotic solvents, hydrophobic and aprotic solvents or mixtures thereof. Here, examples of the hydrophobic solvent include halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; hydrocarbons such as hexane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; chlorobenzene, And halogenated aromatic hydrocarbons such as dichlorobenzene; esters such as ethyl acetate, butyl acetate, and ethyl benzoate; Examples of the aprotic solvent include ketones such as acetone and methyl ethyl ketone; ethers such as diethyl ether, diisopropyl ether and dimethoxyethane; nitrogen compounds such as acetonitrile, dimethylacetamide and hexamethylphosphoric triamide; carbon disulfide; Sulfur compounds such as dimethyl sulfoxide; phosphorus compounds such as hexamethylphosphoramide; and combinations thereof. Solvents preferably used include alcohol solvents such as methanol, ethanol, n-propanol, n-butanol and t-butanol, ketone solvents such as acetone and methyl ethyl ketone, diethyl ether, diisopropyl ether, tetrahydrofuran and 1,4-dioxane. Ether solvents, halogenated hydrocarbon solvents such as methylene chloride and 1,1,2-trichloroethane, and nitrogen compounds such as acetonitrile, particularly preferably methanol, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, methylene chloride and acetonitrile. .

The density | concentration of the pigment | dye in a pigment | dye solution can be suitably adjusted with the pigment | dye to be used, the kind of solvent, and a pigment | dye adsorption process, for example, 1 * 10 < ^-5 > mol / liter or more, Preferably it is 5 * 10 < ^-5 > -1 *. About 10 ⁻² mol / liter is mentioned.

  Note that if the amount of dye adsorbed is small, the sensitizing effect will be insufficient. Conversely, if the amount of adsorbed is large, the dye not adsorbed on the oxide semiconductor will float, which will reduce the sensitizing effect and increase the photoelectric conversion efficiency. This is not preferable because it causes a decrease. From the above, it is preferable to quickly remove the unadsorbed dye by washing. As the cleaning solvent, a solvent having relatively low solubility of the dye and easy to dry is preferable. Moreover, it is preferable to perform washing in a heated state. In addition, after removing excess dye by washing, the surface of the oxide semiconductor fine particles may be treated with an organic basic compound to promote removal of unreacted dye in order to make the adsorption state of the dye more stable. Good. Examples of the organic basic compound include derivatives such as pyridine and quinoline. When these compounds are liquid, they may be used as they are, but when they are solid, they may be dissolved in a solvent, preferably the same solvent as the dye solution.

  When two or more dyes of the present invention are used, the ratio of the dyes to be mixed is not particularly limited and is optimized and selected from the respective dyes. Generally, from the equimolar mixture, 10% per dye. It is preferable to use about mol or more. As a specific method when two or more kinds of dyes are used in combination, the dyes may be adsorbed on the semiconductor layer sequentially or may be mixed and dissolved. Moreover, the structure which laminates | stacks the semiconductor which adsorb | sucked the pigment | dye previously at a post process may be sufficient. When the dye is adsorbed to the oxide semiconductor layer using a solution in which the dye to be used in combination is mixed and dissolved, the total concentration of the dye in the solution may be the same as when only one kind is supported. As a solvent in the case of using a mixture of dyes, the above-mentioned solvents can be used. Even when a solution is prepared for each dye to be used in combination and adsorbed to the semiconductor layer, the solvent described above can be used as the solvent, and the solvent for each dye to be used may be the same or different. When preparing a separate solution for each dye and immersing in each solution in order, the surface layer of the semiconductor layer on which the first dye is immersed and adsorbed is lightly washed with a good solvent for the dye. Multilayer adsorption can be achieved by immersion adsorption of the two dyes.

  When the dye is supported on the thin film of oxide semiconductor fine particles, it is effective to support the dye in the presence of the inclusion compound in order to prevent the association between the dyes. Examples of inclusion compounds include steroidal compounds such as cholic acid, crown ether, cyclodextrin, calixarene, polyethylene oxide, and the like. Deoxycholic acid, dehydrodeoxycholic acid, chenodeoxycholic acid, methyl cholate are preferable. Examples include esters, cholic acids such as sodium cholate, polyethylene oxide, and the like. Further, after the dye is supported, the surface of the semiconductor layer may be treated with an amine compound such as 4-t-butylpyridine. As a treatment method, for example, a method in which a substrate provided with a semiconductor fine particle thin film carrying a dye in an ethanol solution of amine is immersed.

<Conductive substrate>
The conductive substrate 1 used in the present invention is preferably substantially transparent, and it is important that it is a so-called transparent conductive substrate. “Substantially transparent” means that the light transmittance is 10% or more, preferably 50% or more, and particularly preferably 80% or more. As the conductive substrate, a substrate having conductivity per se, or a substrate having a conductive layer on the surface thereof can be used. In the latter case, it is possible to use a glass plate, a ceramic polishing plate such as titanium oxide or alumina, and various known plastic sheets as the substrate.

  Specific examples of the plastic sheet include triacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), syndiotactic polyester (SPS), and polycarbonate (PC). , Polyarylate (PA), polyetherimide (PEI), polysulfone (PSF), polyethersulfone (PES), cyclic polyolefin, phenoxy resin, brominated phenoxy and the like. In the present invention, since it is exposed to a high temperature in the plasma irradiation step, it is preferable to use a plastic sheet having a higher softening point, and the softening point is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. The softening point can be evaluated by measuring the Vicat softening point of JIS-K7206.

  In FIG. 1, the conductive material used for the conductive layer 12 provided on the light-transmitting substrate 11 is an inorganic conductive material, polymer-based conductive material, or inorganic-organic composite made of various known metals and metal oxides. Any type of conductive material can be used, such as a conductive material of a type, or a conductive material in which these are arbitrarily mixed.

Specific examples of the inorganic conductive material include metals such as platinum, gold, silver, copper, zinc, titanium, aluminum, rhodium, and indium, conductive carbon, tin-doped indium oxide (ITO), and tin oxide (SnO ₂ ). And metal oxides such as fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), and zinc oxide (ZnO ₂ ). Specific examples of the polymer-based conductive material include conductive polymers obtained by polymerizing various derivatives such as thiophene, pyrrole, furan, and aniline, and polyacetylene. Polythiophene is preferable from the viewpoint of high conductivity, Polyethylene dioxythiophenes (PEDOT / PSS) are particularly preferable.

  As a method for forming a conductive layer on a substrate, a known appropriate method according to a conductive material can be used. For example, when a conductive layer made of a metal oxide such as ITO is formed, a sputtering method is used. And thin film forming methods such as CVD, SPD (spray pyrolysis deposition) and vapor deposition. Further, when forming a conductive layer made of a polymer-based conductive material, it is preferably formed by various known coating methods.

  The thickness of the conductive layer is preferably about 0.01 μm to 10 μm, more preferably about 0.05 μm to 5 μm.

The lower the surface resistance of the conductive substrate, the better. Specifically, it is preferably 50 Ω / cm ² or less, more preferably 10 Ω / cm ² or less.

  In addition, in order to improve the current collection efficiency of the conductive substrate and further increase the conductivity, the area ratio in a range that does not significantly impair the light transmittance, gold, silver, copper, platinum, aluminum, nickel, indium, titanium, A metal wiring layer made of tungsten or the like may be used in combination with the conductive layer. In the case of using a metal wiring layer, it is preferable that light is uniformly transmitted through the conductive base material as a pattern such as a lattice shape, a stripe shape, or a comb shape. When a metal wiring layer is used in combination, it is preferable to install the conductive layer on the substrate by vapor deposition, sputtering, or the like.

  In a dye-sensitized solar cell, in order to suppress a decrease in open circuit voltage due to a short circuit between the conductive layer provided on the light-transmitting substrate and the electrolyte sealed in the cell, It is preferable to form a metal oxide or the like on the order of several nm to several tens of nm. Specifically, titanium oxide, zinc oxide, tin oxide, indium oxide, niobium oxide, tungsten oxide, zirconium oxide, strontium titanate, barium titanate, calcium titanate, etc. can be raised, and these are mixed alone or in combination. It is desirable to form the film using a vacuum deposition method, a sputtering method, a CVD method, a dip coating method, or the like.

<Charge transfer layer>
The charge transfer layer is a layer containing a charge transport material having a function of replenishing electrons to the oxidant of the dye. Examples of typical charge transport materials that can be used in the present invention include a solvent in which a redox counter ion is dissolved, an electrolytic solution such as a room temperature molten salt containing the redox counter ion, and a solution of the redox counter ion as a polymer. Examples thereof include a gel-like quasi-solidified electrolyte impregnated with a matrix, a low-molecular gelling agent, and the like, and a polymer solid electrolyte. In addition to charge transport materials that involve ions, electron transport materials and hole transport materials can also be used as materials whose carrier transport in solids is involved in electrical conduction, and these can be used in combination. Is possible.

  When using an electrolytic solution for the charge transfer layer, the redox counter ion contained is not particularly limited as long as it can be used in a generally known solar cell.

Specifically, those containing a redox counter ion such as I ⁻ / I ³⁻ and Br ²⁻ / Br ^{3 −} , ferrocyanate / ferricyanate, ferrocene / ferricinium ion, cobalt Examples include metal redox systems such as metal complexes such as complexes, organic redox systems such as alkylthiol-alkyldisulfides, viologen dyes, hydroquinone / quinone, and sulfur compounds such as sodium polysulfide and alkylthiol / alkyldisulfides. . More specifically as iodine, iodine and LiI, NaI, KI, CsI, a combination of a metal iodide such as CaI _2, tetraalkylammonium iodide, pyridinium iodide, quaternary ammonium compounds such as imidazolium iodide And combinations with iodine salts of quaternary imidazolium compounds. More specifically, bromine-based combinations include bromine and metal bromides such as LiBr, NaBr, KBr, CsBr, and CaBr ₂ , and combinations of bromides of quaternary ammonium compounds such as tetraalkylammonium bromide and pyridinium bromide. Can be mentioned.

  As a solvent, it is an electrochemically inert compound that has low viscosity and improved ion mobility, or has a high dielectric constant and improved effective carrier concentration, and can exhibit excellent ionic conductivity. Is desirable. Specifically, carbonate compounds such as dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether compounds such as dioxane, diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl Ethers, chain ethers such as polyethylene glycol dialkyl ether, polypropylene glycol dialkyl ether, alcohols such as methanol, ethanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, Ethylene glycol, diethylene glycol, Polyhydric alcohols such as reethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerin, nitrile compounds such as acetonitrile, glutarodinitrile, propionitrile, methoxypropionitrile, methoxyacetonitrile, benzonitrile, tetrahydrofuran, dimethylsulfur Aprotic polar substances such as foxide and sulfolane can be used.

  A preferable electrolyte concentration is 0.1 M / L or more and 15 M / L or less, and more preferably 0.2 M / L or more and 10 M / L or less. Moreover, the preferable addition density | concentration of an iodine when using an iodine type is 0.01 M / L or more and 0.5 M / L or less.

  The molten salt electrolyte is preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. Examples of the molten salt electrolyte include pyridinium salts described in WO95 / 18456, JP-A-8-259543, JP-A-2001-357896, Electrochemistry, Vol. 65, No. 11, page 923 (1997), and the like. And electrolytes containing known iodine salts such as imidazolium salts and triazolium salts. These molten salt electrolytes are preferably in a molten state at room temperature, and it is preferable not to use a solvent.

  Gels prepared by adding an electrolyte or electrolyte solution to an oligomer or polymer matrix, polymer addition, addition of low-molecular gelling agent or oil gelling agent, polymerization including polyfunctional monomers, polymer crosslinking reaction, etc. (Pseudo-solidification) can also be used. In the case of gelation by adding a polymer, polyacrylonitrile and polyvinylidene fluoride can be preferably used. In the case of gelation by adding an oil gelling agent, a preferred compound is a compound having an amide structure in the molecular structure. Further, when the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a crosslinkable reactive group and a crosslinking agent in combination. In this case, a preferable crosslinkable reactive group is a nitrogen-containing heterocyclic ring (for example, a pyridine ring, an imidazole ring, a thiazole ring, an oxazole ring, a triazole ring, a morpholine ring, a piperidine ring, a piperazine ring), and a preferable crosslinking agent. Is a bifunctional or higher functional reagent (for example, alkyl halide, halogenated aralkyl, sulfonate ester, acid anhydride, acid chloride, isocyanate, etc.) capable of electrophilic reaction with a nitrogen atom. The concentration of the electrolyte is usually 0.01 to 99% by mass, and preferably about 0.1 to 90% by mass.

In addition, as the gel electrolyte, an electrolyte composition containing an electrolyte and metal oxide particles and / or conductive particles can also be used. As the metal oxide particles, TiO ₂ , SnO ₂ , WO ₃ , ZnO, ITO, BaTiO ₃ , Nb ₂ O ₅ , In ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , La ₂ O ₃ , SrTiO ₃ , Y Examples thereof include one or a mixture of two or more selected from the group consisting of ₂ O ₃ , Ho ₂ O ₃ , Bi ₂ O ₃ , CeO ₂ , and Al ₂ O ₃ . These may be doped impurities or complex oxides. Examples of the conductive particles include those made of a substance mainly composed of carbon.

  Next, the polymer electrolyte is a solid substance capable of dissolving the redox species or binding with at least one substance constituting the redox species, for example, polyethylene oxide, polypropylene oxide, polyethylene succinate, Polymer functional groups such as poly-β-propiolactone, polyethyleneimine, polyalkylene sulfide, or cross-linked products thereof, polyphosphazene, polysiloxane, polyvinyl alcohol, polyacrylic acid, polyalkylene oxide, Examples include those obtained by adding a polyether segment or oligoalkylene oxide structure as a side chain or a copolymer thereof. Among them, those having an oligoalkylene oxide structure as a side chain or a polyether segment as a side chain. Those with is preferable.

  In order to contain the redox species in the solid, for example, a method of polymerizing in the coexistence of a monomer that becomes a polymer compound and a redox species, a solid such as a polymer compound is dissolved in a solvent as necessary. Then, the above-described method of adding the redox species can be used. The content of the redox species can be appropriately selected according to the required ion conduction performance.

In the present invention, instead of an ion conductive electrolyte such as a molten salt, a solid hole transport material which is organic or inorganic or a combination of both can be used. Organic hole transport materials include aromatic amines and triphenylene derivatives, polyacetylene and its derivatives, poly (p-phenylene) and its derivatives, poly (p-phenylene vinylene) and its derivatives, polythienylene vinylene and its Conductive polymers such as derivatives, polythiophene and derivatives thereof, polyaniline and derivatives thereof, polytoluidine and derivatives thereof can be preferably used. In order to control the dopant level, the hole transport material may be added with a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate, or the potential control of the oxide semiconductor surface ( A salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added to perform compensation of the space charge layer. A p-type inorganic compound semiconductor can be used as the inorganic hole transport material. The p-type inorganic compound semiconductor for this purpose preferably has a band gap of 2 eV or more, and more preferably 2.5 eV or more. Also, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye-adsorbing electrode from the condition that the holes of the dye can be reduced. Although the preferable range of the ionization potential of the p-type inorganic compound semiconductor varies depending on the dye used, it is generally preferably 4.5 eV or more and 5.5 eV or less, and more preferably 4.7 eV or more and 5.3 eV or less. . A preferred p-type inorganic compound semiconductor is a compound semiconductor containing monovalent copper, preferably CuI and CuSCN, and most preferably CuI. The preferred hole mobility of the charge transfer layer containing the p-type inorganic compound semiconductor is 10 ⁻⁴ cm ² / V · sec or more and 10 ⁴ cm ² / V · sec or less, and more preferably 10 ⁻³ cm ² / V · sec. sec to 10 ³ cm ² / V · sec. The preferable conductivity of the charge transport layer is 10 ⁻⁸ S / cm or more and 10 ² S / cm or less, and more preferably 10 ⁻⁶ S / cm or more and 10 S / cm or less.

  In the present invention, the method for forming the charge transfer layer 4 between the semiconductor electrode and the cathode electrode 5 is not particularly limited. For example, the semiconductor electrode and the cathode electrode are disposed opposite to each other, and then both electrodes are disposed. A method of forming the charge transfer layer 4 by filling the above-described electrolyte solution and various electrolytes in between, and forming the charge transfer layer 4 by dropping or coating the electrolyte or various electrolytes on the semiconductor electrode or the cathode electrode, and then charge A method of superimposing the other electrode on the moving layer 4, a method of forming a hole for electrolyte injection in the electrode of the cell sealed except for the charge moving layer, and forming the charge moving layer 4 by injecting the electrolyte therefrom Can be used. In addition, in order to prevent electrolyte from leaking between the semiconductor electrode and the cathode electrode, the gap between the semiconductor electrode and the cathode electrode is sealed with a film or resin as necessary, or the semiconductor electrode and the charge transfer It is also preferable to store the layer 4 and the cathode electrode 5 in an appropriate case.

  In the case of the former forming method, as a method for filling the charge transfer layer, a normal pressure process using capillary action by dipping or the like, or a vacuum process in which the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure can be used. .

  In the latter forming method, microgravure coating, dip coating, screen coating, spin coating or the like can be used as a coating method. In the wet charge transfer layer, the counter electrode is provided in an undried state and measures for preventing liquid leakage at the edge portion are taken. In the case of a gel electrolyte, there is a method in which it is applied in a wet manner and solidified by a method such as polymerization. In this case, the counter electrode can be applied after drying and fixing.

  In the case of a solid electrolyte or a solid hole transport material, a charge transfer layer can be formed by a dry film formation process such as a vacuum deposition method or a CVD method, and then a cathode electrode can be applied. Specifically, it can be introduced into the electrode by techniques such as vacuum deposition, casting, coating, spin coating, dipping, electrolytic polymerization, and photoelectropolymerization, and the substrate can be It is formed by evaporating the solvent by heating to an arbitrary temperature.

The thickness of the charge transfer layer is preferably 10 μm or less, more preferably 5 μm or less, and further preferably 1 μm or less. The conductivity of the charge transfer layer is preferably 1 × 10 ⁻¹⁰ S / cm or more, more preferably 1 × 10 ⁻⁵ S / cm or more.

<Cathode electrode>
As the cathode electrode that can be used in the present invention, a single-layer structure of a substrate having conductivity itself, or a substrate having a counter electrode conductive layer on the surface thereof can be used in the same manner as the conductive substrate described above. . In the latter case, the conductive material and the base material used for the counter electrode conductive layer, and the manufacturing method thereof are the same as those of the conductive base material 1 described above, and various known materials and methods can be applied. Among them, it is preferable to use those having catalytic ability to perform oxidation of I ³ -ion or the like or reduction reaction of other redox ions at a sufficient speed. Specifically, the surface of the platinum electrode or conductive material is used. Examples thereof include platinum-plated or platinum-deposited, rhodium metal, ruthenium metal, ruthenium oxide, and carbon. In view of cost and flexibility as described above, it is also one of preferred embodiments that a plastic sheet is used as a base material and a polymer material is applied as a conductive material.

  The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 nm to 10 μm. When the counter electrode conductive layer is a metal, the thickness is preferably 5 μm or less, and more preferably in the range of 10 nm to 3 μm. The surface resistance of the cathode electrode is preferably as low as possible. Specifically, the range of the surface resistance is preferably 50Ω / □ or less, more preferably 20Ω / □ or less, still more preferably 10Ω / □ or less. .

  Since light may be received from one or both of the conductive substrate 1 and the cathode electrode 5 described above, it is sufficient that at least one of the conductive substrate and the cathode electrode is substantially transparent. From the viewpoint of improving the power generation efficiency, it is preferable to make the conductive base material transparent so that light enters from the conductive base material side. In this case, the cathode electrode preferably has a property of reflecting light. As such a cathode electrode, glass or plastic deposited with a metal or a conductive oxide, or a metal thin film can be used.

  For the cathode electrode, a conductive material is directly applied, plated, or vapor deposited (PVD, CVD) on the above-described charge transfer layer, or a conductive layer side of a base material having a counter electrode conductive layer or a single conductive base material layer is pasted. That's fine. In addition, as in the case of the conductive base material, it is also one of preferred embodiments to use a metal wiring layer in combination, particularly when the cathode electrode is transparent.

  The counter electrode is preferably conductive and has a catalytic action on the reduction reaction of the redox electrolyte. For example, glass, or a polymer film deposited with platinum, carbon, rhodium, ruthenium, etc. and coated with conductive fine particles can be used.

<< Preparation of semiconductor fine particle paste >>
The semiconductor porous membrane layer was prepared by laminating and applying a paste containing semiconductor fine particles on a transparent conductive substrate, drying and baking. Hereinafter, a dispersion paste of semiconductor fine particles was prepared.

[Preparation of paste A]
6 g of acetic acid was added dropwise to 28 g of tetraisopropoxytitanium (manufactured by Tokyo Chemical Industry Co., Ltd.), and after stirring for a while, 150 ml of 0.1M nitric acid was added, and the temperature was raised to 80 ° C. and stirred for 5 hours. 200 ml of pure water was further added to the obtained dispersion, and the mixture was treated in an autoclave containing a titanium cup under a high pressure of 250 ° C. for 12 hours. Then, after intermittently dispersing for 10 minutes using an ultrasonic disperser UH-300 manufactured by SMT, centrifugation and supernatant removal were repeatedly replaced with ethanol. Using a rotary evaporator, the final solid content is adjusted to 15% by mass, 20 g of 30% by mass aqueous polyethylene glycol (Kanto Chemical Co., Ltd., molecular weight 20000) aqueous solution, activator (Kao Co., Emulgen 120) 0.5 g was added. The obtained paste-like dispersion was dispersed using a 3-roll mill EXAKT80 manufactured by EXAK Technologies to prepare semiconductor fine particle dispersion paste A.

[Preparation of paste B]
A semiconductor fine particle dispersion paste B was prepared in the same manner as the paste A, except that 0.38 g of pentaethoxyniobium (manufactured by High Purity Chemical Laboratory) was mixed in addition to the tetraisopropoxytitanium.

[Preparation of paste C]
A semiconductor fine particle dispersion paste C was prepared in the same manner as the paste A except that 0.38 g of tetrabutoxyzirconium (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was mixed in addition to the tetraisopropoxytitanium of the paste A.

[Preparation of paste D]
A semiconductor fine particle dispersion paste D was prepared in the same manner as the paste A, except that 0.76 g of tetrabutoxyzirconium (manufactured by Kojundo Chemical Laboratory Co., Ltd.) was mixed in addition to the tetraisopropoxytitanium of the paste A.

<< Evaluation of energy level of conduction band and LUMO >>
Regarding the pastes A to D produced above, each paste was dried and baked at 500 ° C. for 60 minutes to obtain a semiconductor powder, and a semiconductor valence band (VB) was measured using an ultraviolet photoelectron spectrometer (UPS). In addition, the energy level of the conduction band (CB) was calculated from the difference by separately obtaining the band gap (Eg) from the absorption edge of the diffuse reflection ultraviolet-visible absorption spectrum. As a result, compared to the semiconductor obtained from paste A, paste B was higher, paste C was higher than paste B, and paste D had a higher conduction band energy level than paste C.

  Similarly, the LUMO energy levels of the dyes shown in the following compounds A and B were also estimated. As a result, it was found that the dye had a higher LUMO energy level in the order of compound A <compound B.

<Production of dye-sensitized solar cell>
[Production of SC-01]
A 10 nm semiconductor film was formed on a transparent conductive glass substrate coated with fluorine-doped tin oxide as a conductive layer, using a high-frequency magnetron sputtering apparatus and titanium oxide as a target material. From the top, the paste A was applied by a screen printing method, and after natural drying, a titanium oxide paste for a light reflecting layer (HPW-400C manufactured by Catalyst Chemical Industry Co., Ltd.) was printed in the same manner. The semiconductor porous film formed by the paste A was prepared by overprinting by screen printing so that the film thickness of the semiconductor porous film was about 12 μm and the light reflection layer was 2 μm.

After being naturally dried, it is passed through a drying zone at 150 ° C. for 10 minutes, and the formed semiconductor porous film is shaved so as to be 5 mm × 5 mm (effective area 0.25 cm ² ), and an electric furnace is used. The substrate was baked at 500 ° C. for 60 minutes to form a semiconductor porous film layer made of titanium oxide on the substrate. After firing in an electric furnace, when cooled to about 80 ° C., 3.0 × 10 ⁻³ mol / L of ruthenium complex dye compound A (N719) for dye-sensitized solar cell, acetonitrile: t-butanol = 1 1 was immersed for 24 hours, and after adsorption of the dye, the excess dye was sufficiently washed out with the acetonitrile: t-butanol solution, and vacuum dried to prepare a semiconductor porous film layer on which the dye was adsorbed.

  As a cathode electrode, a hole was formed on the ITO glass substrate for platinum vapor deposition and electrolyte injection. The semiconductor porous membrane layer and the cathode electrode are bonded to each other using a 25 μm-thick sheet spacer / sealing material (SX-1170-25 manufactured by SOLARONIX) having a 6.5 mm square hole, and the cathode electrode is provided. From the electrolyte injection hole, tetrapropylammonium iodide, iodine, and t-butylpyridine were mixed in a mixed solvent of acetonitrile: ethylene carbonate having a volume ratio of 1: 4, each concentration being 0.46 mol / liter, 0 .06 mol / liter, charge transfer layer containing redox electrolyte dissolved so as to be 0.50 mol / liter is injected, the hole is closed with a hot bond, and the cover glass is covered with the above-mentioned sealant from above. Affixed and sealed. An antireflection film (hard coat / antireflection type cellulose film manufactured by Konica Minolta Opto Co., Ltd.) was bonded to the light receiving surface side of the transparent conductive glass substrate in the previous period to prepare a dye-sensitized solar cell sealing cell SC-01.

[Production of SC-02]
In the production of SC-01, the paste A, paste B, and paste C are laminated in order from the transparent conductive glass substrate side so as to have uniform film thicknesses, and the laminated film thickness of the pastes A to C is 12 μm. SC-02 was produced in the same manner as SC-01 except that the semiconductor porous membrane layer was formed.

[Production of SC-03]
SC-03 was prepared in the same manner as SC-01 except that the dye was replaced with the dye shown in Compound B in the preparation of SC-02.

[Production of SC-04]
In the preparation of SC-02, SC-04 was prepared in the same manner as SC-01 except that a 3.0 × 10 ⁻³ mol / L dye solution in which equimolar amounts of Compound A and Compound B were mixed was used. did.

[Production of SC-05]
In the production of SC-04, SC-05 was produced in the same manner as SC-04 except that paste C, paste B, and paste A were laminated in order from the transparent conductive glass substrate side so as to have uniform film thicknesses. .

[Production of SC-06]
In the production of SC-01, the paste A, paste C, and paste D are laminated in order from the transparent conductive glass substrate side so as to have an equal film thickness, and the laminated film thickness of the pastes A, C, and D becomes 12 μm. A semiconductor porous membrane layer was formed as described above, and SC-06 was prepared in the same manner as SC-01 except that the dye was adsorbed in the same manner as SC-04.

[Production of SC-07]
In the preparation of SC-06, after adsorbing the dye shown in Compound A, the vicinity of the surface layer of the semiconductor porous film was washed with acetone, and then 3.0 × 10 ⁻³ mol / kg of the dye shown in Compound B. SC-07 was prepared in the same manner as SC-06 except that it was immersed in a solution of L acetonitrile: t-butanol = 1: 1.

<< Evaluation of photoelectric conversion characteristics of solar cells >>
About the solar cell produced by the above method, the characteristics when irradiated with light of AM1.5 filter and intensity of 100 mW / m ² by solar simulator (manufactured by JASCO Corporation, low energy spectral sensitivity measuring device CEP-25). Three short circuit currents Jsc (mA / cm ² ) and open circuit voltage value Voc (V) were evaluated with the same configuration and fabrication method, and the average values are shown in Table 1. Further, the photoelectric conversion efficiency η (%) was obtained from Jsc, Voc and FF (fill factor) and is also shown in Table 1.

  From Table 1, it can be seen that a dye-sensitized solar cell with higher efficiency can be achieved by carrying out the present invention. Specifically, in Example SC-04 of the present invention, by stacking semiconductor compositions having different energy levels of conductors and using two or more dyes in combination, SC-01 to SC of Comparative Example In particular, improvement in Jsc was observed with respect to -03. The effect of the present invention was also confirmed from the fact that the configuration of Comparative Example SC-05 in which the semiconductor compositions having different energy levels were stacked opposite to SC-04 had the opposite effect as expected. In SC-06, the energy level of the conductor was controlled by changing the amount of the metal dopant, but the effect of the present invention was also obtained with this configuration. Furthermore, in SC-07, it was clarified that the Jsc was further improved by adsorbing the sensitizing dye in multiple layers, and interestingly, the Voc of the extraction voltage was also effective. This is considered to be an effect found for the first time in combination with a dye having an LUMO level optimum for the semiconductor conductor energy level.

FIG. 1 is a schematic cross-sectional view showing the basic structure of the dye-sensitized solar cell of the present invention. FIG. 2 is a diagram simulating the relationship between the conduction band energy level of a semiconductor and the LUMO level of a sensitizing dye according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive base material 11 Light transmissive base material 12 Conductive layer 2 Semiconductor porous membrane layer 21 Light absorption layer 22 Light reflection layer 3 Dye 4 Charge transfer layer 5 Cathode electrode 6 Opposite substrate 7 Sealing material

Claims (6)

An anode electrode in which a layer composed of at least a semiconductor porous film layer on which a sensitizing dye is adsorbed is formed on the surface of a transparent conductive substrate; a cathode electrode facing the semiconductor porous film layer side of the anode electrode; and In the dye-sensitized solar cell having a configuration in which an electrolyte is sealed between the two electrodes of the anode electrode and the cathode electrode, the semiconductor porous film layer has at least two kinds of semiconductors having different energy levels in the conduction band It is laminated so that the energy level of the conduction band decreases stepwise or continuously toward the transparent conductive substrate, and at least two or more types of increase are added to the semiconductor porous film layer. A dye-sensitized solar cell, wherein a dye-sensitizing dye is adsorbed. The dye-sensitized solar cell according to claim 1, wherein the sensitizing dye comprises at least two kinds of dyes having different LUMO levels. The dye-sensitized solar cell according to claim 1 or 2, wherein at least one of the sensitizing dyes is a dye represented by the following general formula (1) or the following general formula (2).

(Wherein X _{11 to} X ₁₄ and X _{21 to} X ₂₆ each independently represent an oxygen atom, a sulfur atom or a selenium atom, and R ₁₂ , R ₁₃ , R ₂₂ and R ₂₃ are each independently Hydrogen atom, alkyl group, cycloalkyl group, alkenyl group, aryl group, heterocyclic group, halogen atom, cyano group, nitro group, hydroxy group, mercapto group, carboxyl group, carbonyl group, oxycarbonyl group, carbamoyl group, alkoxy group , Heterocyclic oxy group, carbonyloxy group, urethane group, sulfoxyl group, sulfonyloxy group, amino group, sulfonylamino group, sulfamoylamino group, acylamino group, ureido group, sulfonyl group, sulfamoyl group, alkylthio group, arylthio group Or a heterocyclic thio group, and these substituents are further substituted by the substituents shown above. May be. Moreover, R _12, R _13, and R _22, R ₂₃ good .R ₁₄ be bonded to form a ring structure, respectively represent a -COOH group or a -PO ₃ H ₂ group , R ₂₄ and R _{26 each} represent a hydrogen atom, —COOH group or —PO ₃ H ₂ group, and at least one represents a —COOH group or —PO ₃ H ₂ group, L ₁₁ , L ₂₁ and L ₂₂ represent Each independently represents a methylene group, an ethylene group or a propylene group, R ₁₅ and R _{25 each} represents a substituted or unsubstituted alkyl group, and R ₁₁ and R ₂₁ represent R ₁₂ , R ₁₃ and R ₂₂ , R Represents a group having the same meaning as _23. n represents an integer of 1 to 4.) At least two kinds of semiconductor compositions having different energy levels of the conduction bands are formed by metal doping, and the metal-doped semiconductor composition is made of metal doping of different element types. The dye-sensitized solar cell according to any one of claims 1 to 3. The semiconductor composition of at least 2 or more types from which the energy level of the said conduction band differs is a semiconductor composition from which the doping amount of each metal dopant differs by at least 2 sort (s). The dye-sensitized solar cell described. The at least two or more semiconductor compositions having different energy levels in the conduction band are composed of at least one titanium oxide single composition, and the titanium oxide has the lowest energy level of the conductor. Item 6. The dye-sensitized solar cell according to any one of Items 1 to 5.

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